The invention relates to the field of test systems and more particularly to confidence check circuits for use with built-in or self-testing systems.
With the increasing complexity of many technical systems, such as aircraft generator systems, along with increasing reliability standards, many designers are turning to the use of built in or automatic self-testing equipment. Such equipment has the advantage of automatically testing and indicating the nature of failures in a complex system. However, as the systems themselves increase in complexity the circuits required for self-testing also increase in complexity. Thus, the probability is increased that a failure indication may not represent a failure in a particular system but rather a failure in the built-in test systems. As a result it is considered desirable to have some mechanism for checking the reliability of the built-in test system. An example of one such system is provided in Thomas et al. U.S. Pat. No. 3,864,673. What is required is a method of checking the operation of a built-in test system and the associated condition sensors in a comprehensive manner to a very high confidence level.